1. Field of Invention
The present invention relates to a lubrication apparatus of a high pressure pump for a common rail system and, more particularly, to a lubrication apparatus of a high pressure pump for a common rail system which is configured such that it can realize improved lubrication performance of a frictional junction in which a roller and a shoe come into contact with each other.
2. Description of Related Art
Generally, as shown in FIGS. 1 and 2, a high pressure pump 10 used in a common rail system includes a pump housing 11, a roller 12, a shoe 13, and a plunger 14. Here, in the pump housing 11, a shaft chamber 11a, a roller chamber 11b and a spring chamber 11c are formed in such a way that the chambers communicate with each other.
In the shaft chamber 11a, a cam shaft 21 having a cam 21a is rotatably installed. In the roller chamber 11b, both the roller 12 and the shoe 13 are installed such that they come into contact with the cam 21a. In the spring chamber 11c, a spring 16 is installed using a spring seat 15.
Here, in the high pressure pump 10, the plunger 14 is installed in such a way that a first end thereof comes into contact with the shoe 13 and a second end thereof is located in a fuel compression chamber 17 that is formed between an inlet valve 22 and an outlet valve 23.
The inlet valve 22 is a valve that is installed in a fuel channel connected to a low pressure pump 24, and the outlet valve 23 is a valve that is installed in a fuel channel connected to a common rail 25.
Accordingly, when an engine is operated and the cam shaft 21 is rotated by the output power of the engine, the roller 12 is rotated according to a lift profile of the cam 21a, and pushes the shoe 13. Due to the pushed motion of the shoe 13, the plunger 14 reciprocates rectilinearly. Here, due to the rectilinear reciprocation of the plunger 14, low pressure fuel that has been supplied into the fuel compression chamber 17 through the inlet valve 22 is compressed to become high pressure fuel, and the high pressure fuel is discharged to the common rail 25 through the outlet valve 23.
Meanwhile, in the high pressure pump 10, the roller 12 and the shoe 13 are installed in such a way that they come into contact with each other under high pressure. Accordingly, when a frictional junction M1 in which the roller 12 and the shoe 13 come into contact with each other is not sufficiently lubricated, the contact surfaces of both the roller 12 and the shoe 13 are worn by friction and, occasionally, scuffing may be generated in the contact surfaces by severe friction. In an effort to solve the problems caused by friction, a technique in which the frictional junction M1 between the roller 12 and the shoe 13 is lubricated using fuel of the low pressure pump 24 is used in the related art.
In other words, in the related art, the fictional junction M1 between the roller 12 and the shoe 13 is lubricated by the fuel of the low pressure pump 24 using both a first lubrication channel 31 that connects the low pressure pump 24 to the shaft chamber 11a of the pump housing 11 and a second lubrication channel 32 that connects the shaft chamber 11a to the spring chamber 11c. That is, when the fuel of the low pressure pump 24 has filled the shaft chamber 11a, the fuel fills the spring chamber 11c and is fed to the frictional junction M1 between the roller 12 and the shoe 13, thereby lubricating the frictional junction M1.
However, the above-mentioned related art technique for lubricating the frictional junction M1 is problematic in that the passage through which the lubrication fuel flows to the frictional junction M1 between the roller 12 and the shoe 13 is too long, and so the cam shaft 21 may be operated before the frictional junction M1 between the roller 12 and the shoe 13 has been sufficiently lubricated, and, in the above state, the frictional junction M1 between the roller 12 and the shoe 13 on which a high compression load acts may be worn severely by the friction. Furthermore, scuffing is generated in the frictional junction M1 between the roller 12 and the shoe 13, thereby causing inferiority in the quality of the high pressure pump 10.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.